通过宏观断口分析、扫描电镜微观分析、显微组织分析、化学成分分析、XRD物相分析以及硬度测试等手段查找油田钻杆摩擦焊接头的断裂原因.结果表明:断裂面位于杆头和杆体连接的焊缝处,是典型的脆性断裂;在断裂杆头和杆体近断面处存在大量摩擦焊“灰斑”缺陷,“灰斑”主要组成物为Fe3O4,它大大降低了焊接接头的结合性能,导致钻杆接头在使用中出现脆性断裂.

The fracture reason of a friction welding joint for oil field drill rod was investigated by macro fracture analysis,SEM analysis,microstructure analysis,chemical composition analysis,XRD phase analysis and hardness test.The results show that the fracture surface was located at the connection weld between the rod head and rod body,which was a classical brittle fracture.There were a great number of ‘gray spot’ defects near the fracture surface of the rod head and rod body,which mainly were composed of Fe3O4.The defects were the main reason that reduced the combination ability of welding joint,which resulted in the brittle fracture of the drill rod joint during usage.